Reveal pre-images on a timer

The having pre-image  is currently being checked in FullNode.putTransaction
 to see if pre-image is required.
It's call location is inefficient And that function is only needed by the validator.
Therefore, it is checked using a timer that is called periodically.

source/agora/node/FullNode.d

@@ -217,16 +217,6 @@ public class FullNode : API
             this.network.gossipTransaction(tx);
             this.onAcceptedTransaction();
         }
-
-        if (this.enroll_man.needRevealPreimage(this.ledger.getBlockHeight()))
-        {
-            PreImageInfo preimage;
-            if (this.enroll_man.getNextPreimage(preimage))
-            {
-                this.receivePreimage(preimage);
-                this.enroll_man.increaseNextRevealHeight();
-            }
-        }
     }
 
     /// GET: /has_transaction_hash

source/agora/node/Validator.d

@@ -33,6 +33,8 @@ import scpd.types.Stellar_SCP;
 
 import ocean.util.log.Logger;
 
+import core.time;
+
 mixin AddLogger!();
 
 /*******************************************************************************
@@ -81,6 +83,8 @@ public class Validator : FullNode, API
 
             log.info("Doing network discovery..");
             this.network.discover(required_peer_keys);
+            // call checkRevealPreimage periodically every 10 seconds
+            this.taskman.timer(10.seconds, &this.checkRevealPreimage, Periodic.Yes);
             this.network.startPeriodicCatchup(this.ledger, &this.nominator.isNominating);
         });
     }
@@ -171,4 +175,24 @@ public class Validator : FullNode, API
         foreach (sub_conf; quorum_conf.quorums)
             buildRequiredKeys(filter, sub_conf, nodes);
     }
+
+    /***************************************************************************
+
+        Periodically check for pre-images revelation
+        Increase the next reveal height by revelation period if necessary.
+
+    ***************************************************************************/
+
+    private void checkRevealPreimage () @safe
+    {
+        if (!this.enroll_man.needRevealPreimage(this.ledger.getBlockHeight()))
+            return;
+
+        PreImageInfo preimage;
+        if (this.enroll_man.getNextPreimage(preimage))
+        {
+            this.receivePreimage(preimage);
+            this.enroll_man.increaseNextRevealHeight();
+        }
+    }
 }

source/agora/test/EnrollmentManager.d

@@ -89,21 +89,8 @@ unittest
     txs2.each!(tx => node_1.putTransaction(tx));
     containSameBlocks(nodes, 2).retryFor(8.seconds);
 
-    // Currently a new transaction needs to be sent to trigger
-    // the reveal of a pre-image
-    // See https://github.com/bpfkorea/agora/issues/582
-    Transaction tx =
-    {
-        TxType.Payment,
-        [Input(hashFull(txs2[0]), 0)],
-        [Output(Amount(100), pubkey_1)]
-    };
-    auto signature = gen_key_pair.secret.sign(hashFull(tx)[]);
-    tx.inputs[0].signature = signature;
-    node_1.putTransaction(tx);
-
-    // check if nodes have a pre-image newly sent
-    // during creating transactions for the new block
+    // Check if nodes have a pre-image newly sent
+    // While the timer is running on the taskmanager
     nodes.each!(node =>
         retryFor(node.getPreimage(enroll.utxo_key) != PreImageInfo.init,
             5.seconds));